Likely minimal flow; likely too low for any reasonable whitewater experience.
You could park along S.20th Street, for the shortest carry-out, but it is a high-visibility area (a lot of traffic).
To stay slightly more low-key, there is parking in Wilson park off of S.13th Street. Drive past the first parking area (which faces 13th) to the second parking area. Park all the way back by the woods. When you finish your run, you'll carry about a quarter-mile (either through or alongside the woods) to get to your vehicle.